Adds the --log-to-file command line option.

This sets up writing both the cerr and cout streams to a log file, as well as pulls the log rotation logic out of log_windows.*pp into the general logger.

Note that this is meant for usage on macOS and Linux, not Windows. log_windows.*pp has additional functionality in it, as well as a fair bit related to the --wconsole option.

doc/man/wesnoth.6

@@ -190,6 +190,9 @@ lists defined log domains (only the ones containing
 .I filter
 if used) and exits
 .TP
+.B --log-to-file
+redirects logged output to a file. Log files are created in the logs directory under the userdata folder.
+.TP
 .BI --max-fps \ fps
 the number of frames per second the game can show, the value should be between
 .B 1

src/commandline_options.cpp

@@ -257,6 +257,7 @@ commandline_options::commandline_options(const std::vector<std::string>& args)
 		("log-debug", po::value<std::string>(), "sets the severity level of the specified log domain(s) to 'debug'. Similar to --log-error.")
 		("log-none", po::value<std::string>(), "sets the severity level of the specified log domain(s) to 'none'. Similar to --log-error.")
 		("log-precise", "shows the timestamps in log output with more precision.")
+		("log-to-file", "log output is written to a file rather than to standard error.")
 		;
 
 	po::options_description multiplayer_opts("Multiplayer options");
@@ -268,7 +269,7 @@ commandline_options::commandline_options(const std::vector<std::string>& args)
 		("era", po::value<std::string>(), "selects the era to be played in by its id.")
 		("exit-at-end", "exit Wesnoth at the end of the scenario.")
 		("ignore-map-settings", "do not use map settings.")
-		("label", po::value<std::string>(), "sets the label for AIs.") //TODO is the description precise? this option was undocumented before.
+		("label", po::value<std::string>(), "sets the label for AIs.") // TODO: is the description precise? this option was undocumented before.
 		("multiplayer-repeat",  po::value<unsigned int>(), "repeats a multiplayer game after it is finished <arg> times.")
 		("nogui", "runs the game without the GUI.")
 		("parm", po::value<std::vector<std::string>>()->composing(), "sets additional parameters for this side. <arg> should have format side:name:value.")

src/filesystem.cpp

@@ -583,9 +583,12 @@ static void setup_user_data_dir()
 	create_directory_if_missing(user_data_dir / "data" / "add-ons");
 	create_directory_if_missing(user_data_dir / "saves");
 	create_directory_if_missing(user_data_dir / "persist");
+	create_directory_if_missing(filesystem::get_logs_dir());
 
 #ifdef _WIN32
 	lg::finish_log_file_setup();
+#else
+	lg::rotate_logs(filesystem::get_logs_dir());
 #endif
 }
 
@@ -792,6 +795,11 @@ std::string get_user_data_dir()
 	return get_user_data_path().string();
 }
 
+std::string get_logs_dir()
+{
+	return filesystem::get_user_data_dir() + "/logs";
+}
+
 std::string get_cache_dir()
 {
 	if(cache_dir.empty()) {
@@ -1042,7 +1050,6 @@ filesystem::scoped_istream istream_file(const std::string& fname, bool treat_fai
 filesystem::scoped_ostream ostream_file(const std::string& fname, std::ios_base::openmode mode, bool create_directory)
 {
 	LOG_FS << "streaming " << fname << " for writing.";
-#if 1
 	try {
 		boost::iostreams::file_descriptor_sink fd(bfs::path(fname), mode);
 		return std::make_unique<boost::iostreams::stream<boost::iostreams::file_descriptor_sink>>(fd, 4096, 0);
@@ -1056,9 +1063,6 @@ filesystem::scoped_ostream ostream_file(const std::string& fname, std::ios_base:
 
 		throw filesystem::io_exception(e.what());
 	}
-#else
-	return new bfs::ofstream(bfs::path(fname), mode);
-#endif
 }
 
 // Throws io_exception if an error occurs

src/filesystem.hpp

@@ -165,6 +165,7 @@ void set_user_data_dir(std::string path);
 
 std::string get_user_config_dir();
 std::string get_user_data_dir();
+std::string get_logs_dir();
 std::string get_cache_dir();
 
 struct other_version_dir

src/log.cpp

@@ -21,6 +21,10 @@
  */
 
 #include "log.hpp"
+
+#include "filesystem.hpp"
+#include "mt_rng.hpp"
+
 #include <boost/algorithm/string.hpp>
 
 #include <map>
@@ -30,6 +34,12 @@
 #include <iostream>
 #include <iomanip>
 
+static lg::log_domain log_setup("logsetup");
+#define ERR_LS LOG_STREAM(err,   log_setup)
+#define WRN_LS LOG_STREAM(warn,  log_setup)
+#define LOG_LS LOG_STREAM(info,  log_setup)
+#define DBG_LS LOG_STREAM(debug, log_setup)
+
 namespace {
 
 class null_streambuf : public std::streambuf
@@ -47,27 +57,97 @@ static bool timestamp = true;
 static bool precise_timestamp = false;
 static std::mutex log_mutex;
 
-static std::ostream *output_stream = nullptr;
+static std::ostream *output_stream_ = nullptr;
 
 static std::ostream& output()
 {
-	if(output_stream) {
-		return *output_stream;
+	if(output_stream_) {
+		return *output_stream_;
 	}
 	return std::cerr;
 }
 
+// custom deleter needed to reset cerr and cout
+// otherwise wesnoth segfaults on closing (such as clicking the Quit button on the main menu)
+// seems to be that there's a final flush done outside of wesnoth's code just before exiting
+// but at that point the output_file_ has already been cleaned up
+static std::unique_ptr<std::ostream, void(*)(std::ostream*)> output_file_(nullptr, [](std::ostream*){
+	std::cerr.rdbuf(nullptr);
+	std::cout.rdbuf(nullptr);
+});
+
 namespace lg {
 
-redirect_output_setter::redirect_output_setter(std::ostream& stream)
-	: old_stream_(output_stream)
+/** Helper function for rotate_logs. */
+bool is_not_log_file(const std::string& fn)
 {
-	output_stream = &stream;
+	return !(boost::algorithm::istarts_with(fn, lg::log_file_prefix) &&
+			 boost::algorithm::iends_with(fn, lg::log_file_suffix));
+}
+
+/**
+ * Deletes old log files from the log directory.
+ */
+void rotate_logs(const std::string& log_dir)
+{
+	std::vector<std::string> files;
+	filesystem::get_files_in_dir(log_dir, &files);
+
+	files.erase(std::remove_if(files.begin(), files.end(), is_not_log_file), files.end());
+
+	if(files.size() <= lg::max_logs) {
+		return;
+	}
+
+	// Sorting the file list and deleting all but the last max_logs items
+	// should hopefully be faster than stat'ing every single file for its
+	// time attributes (which aren't very reliable to begin with).
+
+	std::sort(files.begin(), files.end());
+
+	for(std::size_t j = 0; j < files.size() - lg::max_logs; ++j) {
+		const std::string path = log_dir + '/' + files[j];
+		LOG_LS << "rotate_logs(): delete " << path;
+		if(!filesystem::delete_file(path)) {
+			ERR_LS << "rotate_logs(): failed to delete " << path << "!";
+		}
+	}
+}
+
+/**
+ * Generates a unique log file name.
+ */
+std::string unique_log_filename()
+{
+	std::ostringstream o;
+	const std::time_t cur = std::time(nullptr);
+	randomness::mt_rng rng;
+
+	o << lg::log_file_prefix
+	  << std::put_time(std::localtime(&cur), "%Y%m%d-%H%M%S-")
+	  << rng.get_next_random()
+	  << lg::log_file_suffix;
+
+	return o.str();
+}
+
+void set_log_to_file()
+{
+	// get the log file stream and assign cerr+cout to it
+	output_file_.reset(filesystem::ostream_file(filesystem::get_logs_dir()+"/"+unique_log_filename()).release());
+	std::cerr.rdbuf(output_file_.get()->rdbuf());
+	std::cout.rdbuf(output_file_.get()->rdbuf());
+}
+
+redirect_output_setter::redirect_output_setter(std::ostream& stream)
+	: old_stream_(output_stream_)
+{
+	output_stream_ = &stream;
 }
 
 redirect_output_setter::~redirect_output_setter()
 {
-	output_stream = old_stream_;
+	output_stream_ = old_stream_;
 }
 
 typedef std::map<std::string, int> domain_map;

src/log.hpp

@@ -61,6 +61,15 @@
 
 namespace lg {
 
+// Prefix and extension for log files. This is used both to generate the unique
+// log file name during startup and to find old files to delete.
+const std::string log_file_prefix = "wesnoth-";
+const std::string log_file_suffix = ".log";
+
+// Maximum number of older log files to keep intact. Other files are deleted.
+// Note that this count does not include the current log file!
+const unsigned max_logs = 8;
+
 enum severity
 {
 	LG_ERROR=0,
@@ -117,6 +126,11 @@ std::string list_logdomains(const std::string& filter);
 void set_strict_severity(int severity);
 void set_strict_severity(const logger &lg);
 bool broke_strict();
+void set_log_to_file();
+
+bool is_not_log_file(const std::string& filename);
+void rotate_logs(const std::string& log_dir);
+std::string unique_log_filename();
 
 // A little "magic" to surround the logging operation in a mutex.
 // This works by capturing the output first to a stringstream formatter, then

src/log_windows.cpp

@@ -44,91 +44,12 @@ static lg::log_domain log_setup("logsetup");
 #define LOG_LS LOG_STREAM(info,  log_setup)
 #define DBG_LS LOG_STREAM(debug, log_setup)
 
-namespace filesystem
-{
-
-std::string get_logs_dir()
-{
-	return filesystem::get_user_data_dir() + "/logs";
-}
-
-}
-
 namespace lg
 {
 
 namespace
 {
 
-// Prefix and extension for log files. This is used both to generate the unique
-// log file name during startup and to find old files to delete.
-const std::string log_file_prefix = "wesnoth-";
-const std::string log_file_suffix = ".log";
-
-// Maximum number of older log files to keep intact. Other files are deleted.
-// Note that this count does not include the current log file!
-const unsigned max_logs = 8;
-
-/** Helper function for rotate_logs. */
-bool is_not_log_file(const std::string& fn)
-{
-	return !(boost::algorithm::istarts_with(fn, log_file_prefix) &&
-			 boost::algorithm::iends_with(fn, log_file_suffix));
-}
-
-/**
- * Deletes old log files from the log directory.
- */
-void rotate_logs(const std::string& log_dir)
-{
-	std::vector<std::string> files;
-	filesystem::get_files_in_dir(log_dir, &files);
-
-	files.erase(std::remove_if(files.begin(), files.end(), is_not_log_file), files.end());
-
-	if(files.size() <= max_logs) {
-		return;
-	}
-
-	// Sorting the file list and deleting all but the last max_logs items
-	// should hopefully be faster than stat'ing every single file for its
-	// time attributes (which aren't very reliable to begin with.
-
-	std::sort(files.begin(), files.end());
-
-	for(std::size_t j = 0; j < files.size() - max_logs; ++j) {
-		const std::string path = log_dir + '/' + files[j];
-		LOG_LS << "rotate_logs(): delete " << path;
-		if(!filesystem::delete_file(path)) {
-			WRN_LS << "rotate_logs(): failed to delete " << path << "!";
-		}
-	}
-}
-
-/**
- * Generates a "unique" log file name.
- *
- * This is really not guaranteed to be unique, but it's close enough, since
- * the odds of having multiple Wesnoth instances spawn with the same PID within
- * a second span are close to zero.
- *
- * The file name includes a timestamp in order to satisfy the requirements of
- * the rotate_logs logic.
- */
-std::string unique_log_filename()
-{
-	std::ostringstream o;
-
-	o << log_file_prefix;
-
-	const std::time_t cur = std::time(nullptr);
-	o << std::put_time(std::localtime(&cur), "%Y%m%d-%H%M%S-");
-
-	o << GetCurrentProcessId() << log_file_suffix;
-
-	return o.str();
-}
-
 /**
  * Returns the path to a system-defined temporary files dir.
  */
@@ -291,7 +212,7 @@ private:
 };
 
 log_file_manager::log_file_manager(bool native_console)
-	: fn_(unique_log_filename())
+	: fn_(lg::unique_log_filename())
 	, cur_path_()
 	, use_wincon_(console_attached())
 	, created_wincon_(false)
@@ -531,7 +452,7 @@ void finish_log_file_setup()
 		log_init_panic(std::string("Could not create logs directory at ") +
 					   log_dir + ".");
 	} else {
-		rotate_logs(log_dir);
+		lg::rotate_logs(log_dir);
 	}
 
 	lfm->move_log_file(log_dir);

src/log_windows.hpp

@@ -39,16 +39,6 @@
  * and later versions, requiring UAC virtualization to be enabled).
  */
 
-namespace filesystem
-{
-
-/**
- * Returns the path to the permanent log storage directory.
- */
-std::string get_logs_dir();
-
-}
-
 namespace lg
 {
 

src/wesnoth.cpp

@@ -986,12 +986,18 @@ int main(int argc, char** argv)
 	assert(!args.empty());
 
 	// --nobanner needs to be detected before the main command-line parsing happens
+	// --log-to needs to be detected so the logging output location is set before any actual logging happens
 	bool nobanner = false;
 	for(const auto& arg : args) {
 		if(arg == "--nobanner") {
 			nobanner = true;
 			break;
 		}
+#ifndef _WIN32
+		else if(arg == "--log-to-file") {
+			lg::set_log_to_file();
+		}
+#endif
 	}
 
 #ifdef _WIN32